1. Field of the Invention
The present invention relates to an etchant composition, method of patterning a conductive layer, and manufacturing a flat panel display device using the same. More particularly, the present invention relates to an etchant composition for simultaneously etching aluminum, molybdenum, and aluminum alloy and methods of patterning a conductive layer and manufacturing a flat panel display device using the same.
2. Description of the Related Art
In the prior art, an etchant that includes phosphoric acid, nitric acid, acetic acid and water is typically used to etch aluminum-based conductive material. An additive could be added to the etchant. However, this conventional etchant has a number of disadvantages.
First, because of irregular surface reaction, accurate and fine pattern of conductive material couldn't be formed. After 24 hours, the nitric acid portion in the etchant shows a sharp fall in concentration, negatively affecting surface uniformity. Furthermore, tip phenomenon occurs quite frequently. In a tip phenomenon, some part of a metal that is supposed to be etched does not get. Due to these problems, productivity decreases.
If the etchant includes more than 5 weight % of nitric acid in the composition, tip phenomenon could be prevented. However, to produce an accurate, fine pattern in the conductive layer, excessive etching of the lateral part of the conductive material is minimized. Too much nitric acid in the etchant causes damage to photo-resist and accelerates lateral etching.
Especially, in case of a multi-layer structure composed of different conductive materials having different etching rates, the problem becomes more serious because each layer may have to be etched by a different etchant, the process for etching the multi-layer may use different etching equipment for each layer, and the etching process for each layer can not be conducted at the same time. As a consequence, etching process gets complicated and manufacturing cost and time increases. Even if the same etchant is used for etching the multi-layer structure, tip phenomenon could have due to different etching rate of each conductive material and galvanic effect, resulting in an etching quality that is not sufficiently high. For the above reasons, there are many challenges to etching a multi-layer structure in an efficient manner (e.g., with the same etchant for each layer).
These days, there is ever-increasing pressure to simplify and optimize manufacturing processes and pattern uniformity. For example, TFT panel manufacturing process has changed into 4 mask process from 5 mask process. Hence, it is a method of etching a multi-layer structure efficiently is desirable.